I-Dominion Group
Kuhlumbanwa bona iinrhirirhiri ze-Dominion group zasalela ematjeni nofana ehlabathini eminyakeni engaba yi 3.07 bhiliyoni eyadlulako, esikhisini esinamabharasi amabili aqaleneko (rift valley) esabunjwa lokha i-crust engaphasi kwe-craton ithoma ukurega. Ukwehla lokhu kwazala ama-igneous intrusion abuya ku-mantle. Amanye wamalarha we-Dominion Group amumethe iinsalela zegolide, ezamayiniwa ngekulu ipumelelo.
Akukho okhunye okunengi okwaziwako nge-Dominion Group, njengombana koke lokhu kwenzeka esikhathi iside esadlulako begodu kuneendawo ezimbalwa lapho amatje lawa abulungwe kuhle khona. Isibonelo, endaweni ye-Vredefort, ama-Dominion Group atjengiswa ngelarha elondileko le-lava elivela endaweni yinye nofana ezimbili.
Ngemva kobana i-Dominion Group yabekwa phasi, igcenye ye-Kaapvaal craton yathula bese kwathi zoke iinkotlela ebegade ziphasi zangenelela emanzini. Lokhu kwabumba ilwandle elikhulu, elingatjhingeli khulu elingalingana nekhontinendi yoke begodu kwathoma kwasalela iinrhirirhiri ezinengi. Kulesi isigaba, kuyinto ehle ukuqalisisa kuhle indima edlalwa mamanzi ekuhleleni kuhle iinrhirirhiri.
I-Witwatersrand Supergroup
Ngokwesisekelo, amanzi egade ageleza arhurhula ama-fragments emthonjeni wamatje. Ibelo lamanzi esikhathini esinengi linikela ibanga ama-fragments azolikhamba. Lokha imilambo nayitjhayisana namanzi amakhulu (afana namalwandle nofano ichibi), ibelo ageleza ngalo liyehla khudlwana begodu ama-particles amanengi amakhulu ehlela phasi bekacwile aye ngaphasi. Ama-particles afeyini, afana nesanda kunye nedaka, asala emanzini isikhatjhana begodu asalele kude kuneqadi kwamanzi. Isizathu sokobana ngikutjele koke lokhu okukarisako sizokuzwisiseka muva.
Ngalokho, eminyakeni engaba yi 2.97 yamabhiliyoni eyadlulako, amalarha ambalwa weenrhirirhiri zamatje bekasele phasi elwandle elingatjhingeli khulu egade lingalingana iindawo zangaphakathi zoke zeSewula Afrika namhlanjesi. Lokhu kubizwa nge-West Rand Group begodu enza ama-topographical features ambalwa akarisako, afana ne- eponymous Witwatersrand ridge ekhamba hlangana ne-Germiston kunye ne-Krugersdorp.
Ngemva kwesikhathi, i-craton yaphakama kancani bese inarha yabophana yabamlandelande wompomporima kunye nezitja. Imilambo kwanjesi ikhamba eendaweni eziphakemeko etlhagwini netjingalanga ukuya emilandelandeni yamachibi nemehlelo, lapho egade kuneensaleka khona khulu ematjeni nofana ehlabathini. Amatje abumbeka ngalesi isikhathi abizwa nge- Central Rand Group. Ngokuhlanganyela, i-West Rand Group kunye ne-Central Rand Group zibizwa nge-Witwatersrand Supergroup.
Ijiyoloji Eyifihlakalo
I-Central Rand Group beyikhethekile, ngombana iinthoro ezikulu zegolide bezisala zisalela lapho umlambo uthela khona, eqadi kwegerebula. Lokhu kwenza bona kube nommango wegolide onothe khulu ephasini, umumethe igolide elingalingana nesiqunto segolide lephasi loke. Muva, amalarha wamatje lawo (abizwa nge-reef) egade amumethe igolide agujwa ngekulu ipumelelo. Umthombo wamambala owanikela igolide leli, nanamhlanje usesiyifihlo yejiyoloji engaziwako.
Eminyakeni engaba yi 2.7 yamabhiliyoni eyadlulako, i-Kaapvaal Craton yatjhayisana ne-Zimbabwe craton ukuya etlhagwini. Lokhu kwenza iintaba ezikulu ezavela phezulu kwalapho esikubiza ngeLimpopo belt. Yabuye yabanomphumela wokobana i-lava ekulu iphume amabharasini wama-cratons, eyambesa amatje we-Witwatersrand Supergroup. Ama-lava lawa abumba ilarha langaphasi le-Ventersdorp Supergroup.
I-Transvaal Supergroup
Ukuragela phambili, eminyakeni eyi 2.5 bhiliyoni eyadlulako, i-Kaapvaal Craton yathula godu begodu kwabasengathi ibuyele ngaphasi kwelwandle elikhulu. Lokhu kwasisusa sezinye iinrhirirhi ezikulu ezatshwaya isithomo se-Transvaal Supergroup. Lokhu kwabuye kwathomana nesiphetho se-Archaean nesithomo sesikhathi somlando we-Proterozoic, esathatha isikhathi esingaba minyaka eyi 570 yeengidi eyadlulako.
I-Transvaal Supergroup siqubuthu samatje akarisako. Ilarha eliphasi khulu, elibizwa nge-Black Reef Formation, limumethe umkhondo wegolide. Ngaphezulu kune-Chuniespoort Group. Ilarha leli limumethe ubufakazi bepilo yokuthoma ephasini- photosynthesising cyanobacteria. Kulungile, nanyana kungezwakali kukarisa, kodwana ama-microbial critters akhupha umoya (oxygen) njengomkhiqizo omorosekileko, begodu ongaba nomthelela ekukhuliseni amazinga womoya (oxygen) okhona ephasini. Umoya (oxygen) obuya ku-cyanobacteria wahlangana namanzi welwandle ukwenza ubukhulu obuhlukahlukeneko bama-iron oxides, ekwaletha umphumela wakobana kubenama-iron nama-manganese esiwagubha/mayina namhlanjesi.
Ama-Malmani Dolomites
Amakholoni wemilwane akhula emanzini angatjhingeli khulu, okufana nengeqadi lomlambo elinamatje nofana ihlabathi (coral reefs) asela i-carbon dioxide esemanzini. Lokhu kwabangela i-calcium carbonate bona yenzeke msinya ukudlula isikhathi esilindelekileko, okwambesa ilarha elithambileko elinamathelako lemilwane. Kwaragela phambili kwakhula eminye imilwane phezulu kwelarha le-calcium begodu ihlelo leli laragela phambili ngokuziphindaphinda njalo njalo. Lokhu kwabumba isibumbo esifana nengungu yamakholoni wemilwane, ekwagcina sekungasuthi ziinsalela zeenyamazana ezitholakala ngaphakathi kwamatje esikubiza ngama-stromatolites. Isibonelo sama-stromatolites athusako satholakala endaweni ye-Vredefort besabizwa njengegcenye yeendawo zelifa lephasi (World Heritage Site).
I-calcium carbonate yabumba godu ilarha lamatje abizwa nge-Malmani dolomites. Lezi ziqakathekile ngombana ama-dolomites ngemva kwalokho adliwa mamanzi wangaphasi anganelela ematjeni abharasileko, ukubumba umlandelande wamarholo. Muva godu, amarholo abayindawo yokuqcina lapho abantu bokuthoma (abokhokho) balala khona, abafana no Mrs. Ples kunye no-Little Foot. Iinsalela zomuntu/ zenyamazana ezatholakala ngaphakathi kwamatje ezidumileko e-Cradle of Humankind, Sterkfontein, Makapansgat kunye ne-Taung zavela zoke elarheni lelitjeni elimhlophe eline-calcium elisetjenziselwa ukwakha nofana ukwenza isamende okuthiwa yi-limestone. Kwabanemibono yokobana ukutjhayisana ngamandla kwe-Vredefort kwabanesandla ekwenzeni amatje abumba amarholo, begodu asirhelebha ukurarulula umraro wemvelaphi yabantu.
I-Bushveld Igneous Complex
Ngemva kokutjhiya amatje abizwa nge-Transvaal Supergroup emuva, kwabanokuraramba okuvela ngaphasi komhlaba. Eminnyakeni engaba yi 2.06 yamabhiliyoni eyadlulako, umlandelande wokuthuthumba okukhulu kwaphazamisa ukuthula kwama-cyanobacteria bekwambesa i-Kaapvaal Craton ngelarha lamatje nomlotha. Ngemva kwalokho, enye i-plume esuka ku-mantle yasunduzela phezulu ama-igneous material akatelela ukungenelela kuma-lateral planes ematjeni wangaphasi emlanjeni we-Transvaal, kodwana akhenge afinyelele phasi. Isenzo lesi se-magma chamber saphola kancani kancani besabumba umlandelande wamalarha wamatje abizwa nge-Bushveld Igneous Complex. Ingazala pheze zoke iindawo zangaphakathi kweSewula Afrika begodu isibonelo esikhulu somhlobo wazo ephasini. I-Complex lee imumethe godu amanye ama-deposits amakhulu wephasi we-platinum, chromium, copper, vanadium, titanium kunye ne-nickel.
I-Vredefort Bolide
Kwabese kwenzeka into egade ingakalindeleki ekulu eminyakeni eyi 2.5 yamabhiliyoni eyadlulako, i-bolide ye-Vredefort yeza ivela phezulu yehlela ephasini. Khabe imakhilomitha ambalwa ngobudege begodu ikhamba ngebelo eliphezulu iya esentha ye-Kaapvaal Craton. Amandla atjhayisana ngawo bengekhe wawaqabanga. Amatje ebegade aphasi aphenduka irhasi begodu ne-crust egade ingaphasi khulu yahlanakela, ukunikela abososayentsi abanelwazi ngezejiyoliji isithombe salokho okwenzeka emandulo. I-bolide ye-Vredefort yenze umkariso omkhulu.
Ngemva kokutjhayisa ngamandla, amatje amatja aragela phambili ngokubumbeka eSewula Afrika, begodu woke amahlelo wejiyoloji atlolwe ngaphazulu asaragela phambili nanamhlanjesi. Nomakunjalo, koke okwenzekako okuphathelene nejiyoloji yekhontinendi yoke angeze kwatlolwa koke kuphelele encwadi lee. Kunalokho, kufanele silise ukuqala okwenzeka phasi siqale okwenzeka emafini, ukuthola koke okwenzekako kufikela lapho iphasi liba ngendlela esilibona ngakhona namhlanjesi.
Translated by Busisiwe Skhosana